U.S. patent number 8,068,090 [Application Number 12/034,307] was granted by the patent office on 2011-11-29 for image display medium, image display device, storage medium storing an image display program, and image display method.
This patent grant is currently assigned to Fuji Xerox Co., Ltd.. Invention is credited to Masaaki Abe, Yoshinori Machida, Kiyoshi Shigehiro, Yasufumi Suwabe, Satoshi Tatsuura.
United States Patent |
8,068,090 |
Machida , et al. |
November 29, 2011 |
Image display medium, image display device, storage medium storing
an image display program, and image display method
Abstract
There is provided an image display medium that includes: a pair
of substrates at least one of that is light-transmissive; a liquid
enclosed between the substrates; and three or more types of colored
particles dispersed in the liquid that move in accordance with
electric fields applied between the substrates and have different
colors and charge characteristics, wherein at least one type of the
colored particles has an opposite polarity from at least one other
type of colored particles.
Inventors: |
Machida; Yoshinori (Kanagawa,
JP), Shigehiro; Kiyoshi (Kanagawa, JP),
Suwabe; Yasufumi (Kanagawa, JP), Tatsuura;
Satoshi (Kanagawa, JP), Abe; Masaaki (Kanagawa,
JP) |
Assignee: |
Fuji Xerox Co., Ltd. (Tokyo,
JP)
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Family
ID: |
40095428 |
Appl.
No.: |
12/034,307 |
Filed: |
February 20, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080303778 A1 |
Dec 11, 2008 |
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Foreign Application Priority Data
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Jun 5, 2007 [JP] |
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2007-149240 |
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Current U.S.
Class: |
345/107; 359/296;
345/108 |
Current CPC
Class: |
G09G
3/344 (20130101); G02B 26/026 (20130101); G09G
3/3453 (20130101); G09G 3/2003 (20130101); G02F
1/1681 (20190101); G02F 2201/44 (20130101); G02F
2001/1678 (20130101) |
Current International
Class: |
G09G
3/34 (20060101) |
Field of
Search: |
;345/107 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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A 1-267525 |
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Oct 1989 |
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JP |
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A 2001-312225 |
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Nov 2001 |
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JP |
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A 2005-524865 |
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Aug 2005 |
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JP |
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A 2006-58901 |
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Mar 2006 |
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JP |
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Primary Examiner: Dinh; Duc
Attorney, Agent or Firm: Oliff & Berridge, PLC
Claims
What is claimed is:
1. An image display medium comprising: a pair of substrates at
least one of that is light-transmissive; a liquid enclosed between
the substrates: three or more types of colored particles dispersed
in the liquid that move in accordance with electric fields applied
between the substrates and have different colors and charge
characteristics: and multicolor particles that are enclosed between
the substrates and are shaped as rotatable bodies that rotate in
accordance with an electric field applied between the substrates.
and at least first portions of the multicolor particles offset from
centers of gravity thereof have positive or negative polarity, and
the first portions and at least second portions that are different
from the first portions are respectively different colors, wherein
at least one type of the colored particles have an opposite
polarity from at least one other type of colored particles, and
absolute values of voltages required in order for the respective
colored particles to move, and an absolute value of a voltage
required in order for the multicolor particles to rotate in
accordance with the electric field, are respectively different.
2. The image display medium of claim 1, wherein the three or more
types of colored particles move in accordance with the electric
fields within predetermined voltage ranges, and the respective
predetermined voltage range of each type of colored particle is set
to a range that does not overlap ranges of the other type of
colored particle.
3. The image display medium of claim 1, further comprising a
reflecting member that is enclosed between the substrates and is
colored a predetermined color.
4. The image display medium of claim 3, wherein the reflecting
member is colored white.
5. The image display medium of claim 3, wherein the reflecting
member comprises large-diameter particles that are larger than the
colored particles.
6. The image display medium of claim 3, wherein the reflecting
member is a nonwoven fabric.
7. The image display medium of claim 1, wherein the absolute value
of the voltage required in order for the multicolor particles to
rotate are greater than the absolute values of the voltages
required in order for the respective colored particles to move.
8. The image display medium of claim 1, wherein an average volume
particle diameter of the multicolor particles is greater than an
average volume particle diameter of the colored particles.
9. The image display medium of claim 1, wherein the first portions
of the multicolor particles are positively polarized, the at least
second portions that are different from the first portions are
negatively polarized and the multicolor particles are colored
different colors at respective positively-/negatively-polarized
regions.
10. The image display medium of claim 1, wherein the multicolor
particles are rotatably enclosed in light-transmissive capsules
that are filled with a light-transmissive liquid.
11. The image display medium of claim 1, wherein the liquid
includes a porous body that is light-transmissive and within which
a light-transmissive liquid is filled, the multicolor particles are
rotatably housed within the porous body, and the colored particles
pass between the substrates through holes of the porous body.
12. An image display device comprising: an image display medium
having a pair of substrates at least one of that is
light-transmissive, a liquid enclosed between the substrates, and
three or more types of colored particles dispersed in the liquid
that move in accordance with electric fields applied between the
substrates and have different colors and charge characteristics, at
least one type of the colored particles having an opposite polarity
from at least one other type of colored particles; a voltage
application section that applies a voltage between the substrates;
and a controller that controls the voltage application section in
accordance with image information, wherein the controller controls
the voltage application section so as to selectively apply, between
the substrates, respective voltages required in order for the three
or more types of colored particles to move, by using as a reference
a state in which voltage is applied between the substrates using a
maximum voltage among the voltages required. in order for the three
or more types of colored particles to move, the colored particles
comprises: (a) first particles colored a predetermined first color,
and having positive or negative polarity, (b) second particles
colored a second color that is different from the first color, and
having an opposite polarity to the first particles, absolute values
of voltages required in order for the second particles to move
being smaller than absolute values of voltages required in order
for the first particles to move, and (c) third particles colored a
third color that is different from the first color and the second
color. and having the opposite polarity to the first particles,
absolute values of voltages required in order for the third
particles to move being smaller than the absolute values of the
voltages required in order for the first particles and the second
particles to move, and the controller: (1) controls the voltage
application section so as to apply, between the substrates, a
negative voltage required in order for the first particles to move,
displays the first color when the first particles are
positively-polarized, and displays a seventh color that is a
subtractive color mixture of the second color and the third color
when the first particles are negatively-polarized, (2) controls the
voltage application section so as to apply, between the substrates.
a positive voltage required in order for the third particles to
move in a state in which the first color or the seventh color is
displayed, displays a fourth color that is a subtractive color
mixture of the first color and the third color when the first
particles are positively-polarized, and displays the second color
when the first particles are negatively-polarized, (3) controls the
voltage application section so as to apply, between the substrates,
a positive voltage required in order for the second particles to
move in a state in which the first color or the seventh color is
displayed. displays a fifth color that is a subtractive color
mixture of the first particles, the second particles and the third
particles when the first particles are positively-polarized, and
displays an eighth color when the first particles are
negatively-polarized, (4) controls the voltage application section
so as to apply, between the substrates, a negative voltage required
in order for the third particles to move in a state in which the
fifth color or the eighth color is displayed, displays a sixth
color that is a subtractive color mixture of the first particles
and second particles when the first particles are
positively-polarized, and displays the third color when the first
particles are negatively-polarized, (5) controls the voltage
application section so as to apply, between the substrates,a
positive voltage required in order for the first particles to move,
displays the seventh color when the first particles are
positively-polarized, and displays the first color when the first
particles are negatively-polarized, (6) controls the voltage
application section so as to apply, between the substrates, a
negative voltage required in order for the third particles to move
in a state in which the seventh color or the first color is
displayed, displays the second color when the first particles are
positively-polarized, and displays the fourth color when the first
particles are negatively-polarized, (7) controls the voltage
application section so as to apply, between the substrates, a
negative voltage required in order for the second particles to move
in a state in which the seventh color or the first color is
displayed, displays the eighth color when the first particles are
positively-polarized, and displays the fifth color when the first
particles are negatively-polarized, and (8) controls the voltage
application section so as to apply, between the substrates, a
positive voltage required in order for the third particles to move
in a state in which the eighth color or the fifth color is
displayed, displays the sixth color when the first particles are
positively-polarized, and displays the third color when the first
particles are negatively-polarized.
13. A image display device of comprising: an image display medium
having a pair of substrates at least one of that is
light-transmissive, a liquid enclosed between the substrates, and
three or more types of colored particles dispersed in the liquid
that move in accordance with electric fields applied between the
substrates and have different colors and charge characteristics, at
least one type of the colored particles having an opposite polarity
from at least one other type of colored particles; a voltage
application section that applies a voltage between the substrates;
a controller that controls the voltage application section in
accordance with image information; and multicolor particles that
are enclosed between the substrates and are shaped as rotatable
bodies that rotate in accordance with an electric field applied
between the substrates, and at least first portions of the
multicolor particles offset from centers of gravity of the
multicolor particles are positive or negative polarity, and the
first portions and at least second portions that are different from
the first portions are respectively different colors, wherein, when
absolute values of voltages required in order for the respective
colored particles to move, and an absolute value of a voltage
required in order for the multicolor particles to rotate in
accordance with an electric field, are respectively different, and
the controller controls the voltage application section to
selectively apply, between the substrates, voltages required in
order for the three or more types of the colored particles to move
and a voltage required in order for the multicolor particles to
rotate using as a reference a state in which a maximum voltage is
applied between the substrates among the absolute values of the
voltages required in order for the three or more types of colored
particles to move and the absolute value of the voltage required in
order for the multicolor particles to rotate.
14. A non-transitory computer readable storage medium storing an
image display program causing a computer to execute a processing
for display-driving an image display device, the image display
device having an image display medium including: a pair of
substrates at least one of that is light-transmissive; a liquid
enclosed between the substrates; and three or more types of colored
particles dispersed in the liquid that move in accordance with
electric fields applied between the substrates and have different
colors and polarities, at least one type of the colored particles
being charged to an opposite polarity from at least one other type
of colored particles, and the colored particles including: first
particles colored a predetermined first color, and being positively
polarized, second particles colored a second color that is
different from the first color, and being negatively polarized,
absolute values of voltages required in order for the second
particles to move being smaller than absolute values of voltages
required in order for the first particles to move, and third
particles colored a third color that is different from the first
and the second colors, and being negatively polarized , absolute
values of voltages required in order for the third particles to
move being smaller than the absolute values of the voltages
required in order for the first particles and the second particles
to move, and the program causing the computer to execute processing
comprising: a first step of applying, between the substrates, a
negative voltage required in order for the first particles to move,
and displaying the first color when the first particles are
positively polarized, and displaying a seventh color that is a
subtractive color mixture of the second color and the third color
when the first particles are negatively polarized; a second step of
applying, between the substrates, a positive voltage required in
order for the third particles to move in a state in which the first
color or the seventh color is displayed, and displaying a fourth
color that is a subtractive color mixture of the first color and
the third color when the first particles are positively polarized,
and displaying the second color when the first particles are
negatively polarized; a third step of applying, between the
substrates, a positive voltage required in order for the second
particles to move in a state in which the first color or the
seventh color is displayed, and displaying a fifth color that is a
subtractive color mixture of the first particles, the second
particles and the third particles when the first particles are
positively polarized, and displaying an eighth color when the first
particles are negatively polarized; a fourth step of applying,
between the substrates, a negative voltage required in order for
the third particles to move in a state in which the fifth color or
the eighth color is displayed, and displaying a sixth color that is
a subtractive color mixture of the first particles and second
particles when the first particles are positively polarized, and
displaying the third color when the first particles are negatively
polarized; a fifth step of applying, between the substrates, a
positive voltage required in order for the first particles to move,
and displaying the seventh color when the first particles are
positively polarized, and displaying the first color when the first
particles are negatively polarized; a sixth step of applying,
between the substrates, a negative voltage required in order for
the third particles to move in a state in which the seventh color
or the first color is displayed, and displaying the second color
when the first particles are positively polarized, and displaying
the fourth color when the first particles are negatively polarized;
a seventh step of applying, between the substrates, a negative
voltage required in order for the second particles to move in a
state in which the seventh color or the first color is displayed,
and displaying the eighth color when the first particles are
positively polarized, and displaying the fifth color when the first
particles are negatively polarized; and an eighth step of applying,
between the substrates, a positive voltage required in order for
the third particles to move in a state in which the eighth color or
the fifth color is displayed, and displaying the sixth color when
the first particles are positively-polarized, and displaying the
third color when the first particles are negatively-polarized.
15. An image display method for display-driving an image display
device, the image display device having an image display medium
including: a pair of substrates at least one of which is
light-transmissive; a liquid enclosed between the substrates; and
three or more types of colored particles dispersed in the liquid
that move in accordance with electric fields applied between the
substrates and have different colors and polarities, and at least
one type of the colored particles having an opposite polarity from
at least one other type of colored particles, and the colored
particles including: first particles colored a predetermined first
color, and are positively polarized, second particles colored a
second color that is different from the first color, and are
negatively polarized, absolute values of voltages required in order
for the second particles to move being smaller than absolute values
of voltages required in order for the first particles to move, and
third particles colored a third color that is different from the
first color and the second color, and are negatively polarized,
absolute values of voltages required in order for the third
particles to move being smaller than the absolute values of the
voltages required in order for the first particles and the second
particles to move, the method comprising: a first step of applying,
between the substrates, a negative voltage required in order for
the first particles to move, and displaying the first color when
the first particles are positively polarized, and displaying a
seventh color that is a subtractive color mixture of the second
color and the third color when the first particles are negatively
polarized; a second step of applying, between the substrates, a
positive voltage required in order for the third particles to move
in a state in which the first color or the seventh color is
displayed, and displaying a fourth color that is a subtractive
color mixture of the first color and the third color when the first
particles are positively-polarized, and displaying the second color
when the first particles are negatively-polarized; a third step of
applying, between the substrates, a positive voltage required in
order for the second particles to move in a state in which the
first color or the seventh color is displayed, and displaying a
fifth color that is a subtractive color mixture of the first
particles, the second particles and the third particles when the
first particles are positively-polarized, and displaying an eighth
color when the first particles are negatively-polarized; a fourth
step of applying, between the substrates, a negative voltage
required in order for the third particles to move in a state in
which the fifth color or the eighth color is displayed, and
displaying a sixth color that is a subtractive color mixture of the
first particles and second particles when the first particles are
positively-polarized, and displaying the third color when the first
particles are negatively-polarized; a fifth step of applying,
between the substrates, a positive voltage required in order for
the first particles to move, and displaying the seventh color when
the first particles are positively-polarized, and displaying the
first color when the first particles are negatively-polarized; a
sixth step of applying, between the substrates, a negative voltage
required in order for the third particles to move in a state in
which the seventh color or the first color is displayed, and
displaying the second color when the first particles are
positively-polarized, and displaying the fourth color when the
first particles are negatively-polarized; a seventh step of
applying, between the substrates, a negative voltage required in
order for the second particles to move in a state in which the
seventh color or the first color is displayed, and displaying the
eighth color when the first particles are positively-polarized, and
displaying the fifth color when the first particles are
negatively-polarized; and an eighth step of applying, between the
substrates, a positive voltage required in order for the third
particles to move in a state in which the eighth color or the fifth
color is displayed, and displaying the sixth color when the first
particles are positively-polarized, and displaying the third color
when the first particles are negatively-polarized.
Description
CROSS-REFERENCE TO RELATED APPLICATION
This application is based on and claims priority under 35 USC 119
from Japanese Patent Application No. 2007-149240 filed Jun. 5,
2007.
BACKGROUND
1. Technical Field
The present invention relates to an image display medium, an image
display device, a storage medium storing an image display program,
and an image display method.
2. Related Art
Image display media using colored particles are known as
conventional image display media which have a memory property and
which can be rewritten repeatedly. Such an image display medium is
structured to include, for example, a pair of substrates, and
plural types of particle groups having different colors and
different charge characteristics which are enclosed between the
substrates and can move between the substrates due to an applied
electric field. Further, there are also cases in which spacing
members for partitioning the region between the substrate into
plural cells are provided between the substrates for reasons such
as preventing the particles from concentrating at one region
between the substrates.
In such an image display medium, the particles are moved by
voltage, which corresponds to an image, being applied between the
pair of substrates, and the image is displayed as the contrast of
the particles of the different colors. Note that, even after
application of voltage is stopped, the particles remain adhered to
the substrates due to van der Waals force and image force, and the
image display is maintained.
SUMMARY
An aspect of the present invention is an image display medium
having: a pair of substrates at least one of that is
light-transmissive; a liquid enclosed between the substrates; and
three or more types of colored particles dispersed in the liquid
that move in accordance with electric fields applied between the
substrates and have different colors and charge characteristics,
wherein at least one type of the colored particles having an
opposite polarity from at least one other type of colored
particles.
BRIEF DESCRIPTION OF THE DRAWINGS
Exemplary embodiments of the present invention will be described in
detail based on the following figures, wherein:
FIG. 1 is a schematic structural diagram showing an image display
device relating to a first exemplary embodiment;
FIG. 2 is a drawing for explaining application voltages which are
required in order to move colored particles in the image display
device relating to the first exemplary embodiment;
FIG. 3 is a drawing for explaining an example of driving control of
the image display device relating to the first exemplary
embodiment;
FIG. 4 is a flowchart showing an example of the flow of display
driving control of the image display device relating to the first
exemplary embodiment;
FIG. 5 is a drawing for explaining, in the first exemplary
embodiment, driving control in a case in which the magnitudes of
the absolute values of the voltage ranges are set in the order of
yellow particles, magenta particles, and cyan particles, and the
magenta particles, which are second in order of the magnitudes of
the absolute values of the voltage ranges, are made to be the
opposite polarity of the other colored particles;
FIG. 6 is a drawing for explaining, in the first exemplary
embodiment, driving control in a case in which the magnitudes of
the absolute values of the voltage ranges are set in the order of
the cyan particles, the magenta particles, and the yellow
particles, and the yellow particles, which have the smallest
absolute values of the voltage ranges, are made to be the opposite
polarity of the other colored particles;
FIG. 7 is a drawing showing the structure of an image display
device relating to a second exemplary embodiment;
FIG. 8 is a drawing showing a case in which another one type of
colored particles are enclosed between substrates in the image
display device relating to the second exemplary embodiment;
FIG. 9 is a drawing showing an example in which multicolor
particles, which are each painted two or more colors, are used
instead of large-diameter colored particles;
FIG. 10 is a drawing showing an example in which a porous body,
which is structured by silicone rubber in which a migration liquid
such as silicone oil or the like is filled, is used instead of the
dispersion liquid;
FIG. 11 is a drawing showing an example in which bicolor particles
are enclosed, in rotatable states, in transparent capsules which
are filled with a transparent encapsulated migration liquid;
and
FIGS. 12A and 12B are drawings showing examples in which colored
particles and bicolor particles are enclosed in transparent
capsules.
DETAILED DESCRIPTION
Exemplary embodiments of the present invention will be described in
detail hereinafter with reference to the drawings. Note that
members which have substantially the same functions are denoted by
the same reference numerals throughout all of the drawings, and
repeat description thereof may be omitted.
First Exemplary Embodiment
FIG. 1 is a schematic structural diagram showing an image display
device relating to a first exemplary embodiment. Note that FIG. 1
is a drawing showing an example of red display.
As shown in FIG. 1, an image display device 10 relating to the
first exemplary embodiment has an image display medium 12 which is
structured from a display substrate 18 and a back surface substrate
28. The display substrate 18 is formed by a transparent electrode
16 and an obverse layer 17 being laminated on a supporting
substrate 14. The back surface substrate 28 is disposed so as to
oppose the display substrate 18 with a space therebetween, and is
formed by an electrode 22 and an obverse layer 20 being laminated
on a supporting substrate 26.
Three type of colored particles 32 (cyan particles 32C, magenta
particles 32M, and yellow particles 32Y) and a dispersion liquid 24
(a transparent liquid) which is light-transmissive are enclosed
between the display substrate 18 and the back surface substrate 28,
and move electrophoretically between the substrates due to an
electric field which is applied between the substrates. The three
types of colored particles 32 have respectively different charge
characteristics, and at least one type of the colored particles 32
has the opposite polarity. In the present exemplary embodiment, the
cyan particles 32C are positively polarized, and the magenta
particles 32M and the yellow particles 32Y are negatively
polarized. Moreover, in the present exemplary embodiment, the
respective colored particles 32 are particles which move
electrophoretically between the substrates, and have respectively
different absolute values of voltages required to move in
accordance with the electric field. Note that the application
voltages which are required in order for the three types of colored
particles 32 to move can be controlled by, for example, the charge
amount, the particle diameter, or the shape or properties of the
particle surface, or the like.
Pigment particles of a desired color, or resin particles containing
a pigment or dye of a desired color, can be used as the respective
colored particles 32. For example, general pigments or dyes which
are used as printing inks or color toners can be used as the
pigment or dye.
In the present exemplary embodiment, the cyan particles 32C which
are colored cyan, the magenta particles 32M which are colored
magenta, and the yellow particles 32Y which are colored yellow are
used as the colored particles 32, but the colors are not limited to
these. The volume average particle diameter of the respective
colored particles 32 is generally 0.01 .mu.m to 10 .mu.m, and
preferably 0.03 .mu.m to 3 .mu.m, but is not limited to this range.
If the volume average particle diameter of the colored particles 32
is smaller than the above range, there are cases in which the
charge amount of the colored particles 32 may be small, and the
speed of moving through the dispersion liquid 24 may be slow.
Namely, there are cases in which the display responsiveness
deteriorates. Conversely, if the volume average particle diameter
of the colored particles 32 is greater than the aforementioned
range, although the following-property thereof is good, it may be
easy for precipitation due the weight of the colored particles 32
themselves and a deterioration in the memory property to occur.
Note that the volume average particle diameter of the colored
particles 32 is measured by the Laser Scattering Particle Size
Distribution Analyzer LA-920 manufactured by Horiba, Ltd.
The dispersion liquid 24 which is light-transmissive may be an
insulating, colorless, transparent liquid. For example, hydrocarbon
solvents such as silicon, toluene, xylene, isoparaffin, normal
paraffin, and the like can be used.
The transparent electrode 16 and the electrode 22 are respectively
connected to a voltage application section 40. Namely, an electric
field is applied between the substrates due to voltage being
applied to the transparent electrode 16 and the electrode 22 by the
voltage application section 40. Note that it suffices for the
transparent electrode 16 and the electrode 22 to be able to form a
desired electric field between the substrates, and the transparent
electrode 16 and the electrode 22 may be disposed at the exterior
of the image display medium 12 so as to be able to be attached to
and removed from the display substrate 18 and the back surface
substrate 28, respectively.
The voltage application section 40 is connected to a controller 42.
An image storage section 44 is connected to the controller 42.
The controller 42 is structured to include a CPU, a ROM, a RAM, a
hard disk, and the like. The CPU carries out display of images onto
the image display medium 12 in accordance with a program which is
stored in the ROM or the hard disk and the like. The image storage
section 44 is structured by a hard disk or the like, and stores an
image for display which is to be displayed on the image display
medium 12. Namely, due to the controller 42 controlling the voltage
application section 40 and applying voltage to be applied between
the substrates in accordance with the image for display which is
stored in the image storage section 44, the colored particles 32
move in accordance with the voltage and an image is displayed. Note
that the image for display which is stored in the image storage
section 44 may be taken-into the image storage section 44 via a
network or any of various types of recording media such as a
CD-ROM, a DVD, or the like.
Even after the application of voltage between the substrates is
stopped, the colored particles 32 are, maintained in the state of
the time when the voltage was applied, due to van der Waals force
and image force.
FIG. 2 is a drawing for explaining application voltages which are
required in order to move the colored particles 32 in the image
display device relating to the first exemplary embodiment.
As described above, with regard to the application voltages which
are required in order to move the colored particles 32, the
absolute values of the voltages required in order for the
respective colored particles 32 to move in accordance with the
electric field at the time of moving electrophoretically between
the substrates, are respectively different, and at least one type
of the colored particles 32 has the opposite polarity. In more
detail, as shown in FIG. 2, the voltage ranges required in order to
move the respective colored particles 32 are respectively
different. Here, the "voltage range required in order to move the
colored particles" means a voltage range from the voltage required
in order for the particles to start moving, up to a voltage at
which, when the voltage or the voltage application time from the
start of movement is further increased, no chance arises in the
display density and the display density is saturated.
Further, "maximum voltage required in order to move the colored
particles" means a voltage at which, when the voltage or the
voltage application time is further increased from the
aforementioned start of movement, no change arises in the display
density and the display density is saturated. The display density
is the density at the time when, while the optical density (OD) at
the display surface side is measured by a reflection densitometer
(X-Rite 404) manufactured by X-Rite, Incorporated, voltage is
applied between the display surface side and the back surface side,
and the voltage is gradually changed in the direction in which the
measured density increases (the application voltage is increased or
decreased), the chance in density per unit voltage is saturated,
and, even if the voltage or the voltage application time are
increased in this state, no change in density arises and the
density is saturated.
As described above, among the colored particles 32, the cyan
particles 32C are positively polarized, and the magenta particles
32M and the yellow particles 32Y are negatively polarized. The
absolute values of the voltage ranges for moving the respective
colored particles are set in the following order of the magnitudes
thereof: the absolute values |Vc.ltoreq.V.ltoreq.Vc'| (the absolute
values of the values between Vc and Vc') of the voltage range
required in order to move the cyan particles 32C, the absolute
values |Vm.ltoreq.V.ltoreq.Vm| (the absolute values of the values
between Vm and Vm') of the voltage range required in order to move
the magenta particles 32M, and the absolute values
|Vy.ltoreq.V.ltoreq.Vy'| (the absolute values of the values between
Vy and Vy') of the voltage range required in order to move the
yellow particles 32Y Namely, the absolute values of the voltages
required to move the cyan particles 32C are set to be the largest,
and the cyan particles 32C which have the largest absolute value
voltages have the opposite polarity. Further, in the exemplary
embodiment, the respective colored particles 32 can be driven
independently by setting the voltage ranges required in order to
move substantially all of the respective colored particles 32 such
that they do not overlap one another. Note that "substantially all"
means that, because there is dispersion in the characteristics of
the colored particles 32, the characteristics of some of the
colored particles 32 differ to an extent of not contributing to the
display characteristic. Namely, when the voltage or the voltage
application time is further increased from the aforementioned start
of movement, there is a state in which no change arises in the
display density and the display density is saturated.
Next, an example of driving control of the image display device,
which relates to the first exemplary embodiment and is structured
as described above, will be described. Note that, hereinafter, in
order to simplify explanation, description is given with the
electrode 22 at the back surface substrate 28 side being ground (0
V) and voltage being applied to the transparent electrode 16 at the
display substrate 18 side.
First, when the voltage application section 40 applies application
voltage V (-Vc'), which has the largest absolute values of the
voltage ranges required in order to move the respective particles,
between the transparent electrode 16 and the electrode 22 due to
the control of the controller 42, the cyan particles 32C which are
positively polarized move to the display substrate 18 side, and the
magenta particles 32M and the yellow particles 32Y which are
negatively polarized move to the back surface substrate 28 side.
The state (1) in FIG. 3 thereby arises, and cyan is displayed.
Further, when the voltage application section 40 applies the
application voltage V (Vc'), which has the largest absolute values
of the voltage ranges required in order to move the respective
particles, between the transparent electrode 16 and the electrode
22 due to the control of the controller 42, the magenta particles
32M and the yellow particles 32Y which are negatively polarized
move to the display substrate 18 side, and the cyan particles 32C
which are positively polarized move to the back surface substrate
28 side. The state (2) in FIG. 3 thereby arises, and red, which is
a subtractive color mixture of magenta and yellow, is
displayed.
From the state (1) in FIG. 3 (the cyan display state), due to the
voltage application section 40 applying the application voltage V
(Vy') between the transparent substrate 16 and the electrode 22 due
to the control of the controller 42, the yellow particles 32Y move
to the display substrate 18 side. The state (3) in FIG. 3 thereby
arises, and green, which is a subtractive color mixture of cyan and
yellow, is displayed.
From the state (1) in FIG. 3 (the cyan display state), due to the
voltage application section 40 applying the application voltage V
(Vm') between the transparent substrate 16 and the electrode 22 due
to the control of the controller 42, the magenta particles 32M and
the yellow particles 32Y move to the display substrate 18 side. The
state (4) in FIG. 3 thereby arises, and black or grey, which is a
subtractive color mixture of cyan, magenta and yellow, is
displayed.
From the state (4) in FIG. 3 (the black or grey display state), due
to the voltage application section 40 applying the application
voltage V (-Vy') between the transparent substrate 16 and the
electrode 22 due to the control of the controller 42, the yellow
particles 32Y move to the back surface substrate 28 side. The state
(5) in FIG. 3 thereby arises, and blue, which is a subtractive
color mixture of cyan and magenta, is displayed.
From the state (2) in FIG. 3 (the red display state), due to the
voltage application section 40 applying the application voltage V
(-Vm') between the transparent substrate 16 and the electrode 22
due to the control of the controller 42, the magenta particles 32M
and the yellow particles 32Y move to the back surface substrate 28
side. The state (6) in FIG. 3 thereby arises, and a non-display
state arises. Note that, at this time, if the dispersion liquid 24
is colored, the color of the dispersion liquid 24 is displayed. For
example, if the dispersion liquid 24 is colored to white, white
display becomes possible.
From the state (6) in FIG. 3 (the non-display state), due to the
voltage application section 40 applying the application voltage V
(Vy') between the transparent substrate 16 and the electrode 22 due
to the control of the controller 42, the yellow particles 32Y move
to the display substrate 18 side. The state (7) in FIG. 3 thereby
arises, and yellow is displayed.
From the state (2) in FIG. 3 (the red display state), due to the
voltage application section 40 applying the application voltage V
(-Vy') between the transparent substrate 16 and the electrode 22
due to the control of the controller 42, the yellow particles 32Y
move to the back surface substrate 28 side. The state (8) in FIG. 3
thereby arises, and magenta is displayed.
FIG. 4 is a flowchart showing an example of the flow of display
driving control of the image display device relating to the first
exemplary embodiment. Note that the display driving control shown
in FIG. 4 may be carried out by a hardware structure such as a
circuit board or the like, or may be carried out by a software
structure such as a program that causes a computer to execute
processing. Further, in the same way as described above,
description will be given with the electrode 22 at the back surface
substrate 28 side being ground (0 V) and voltage being applied to
the transparent electrode 16 at the display substrate 18 side.
For example, as shown in FIG. 4, on the basis of the image for
display which is stored in the image storage section 44, the
controller 42 determines whether or not cyan is to be displayed
(100). If cyan is to be displayed, the application voltage V (-Vc')
is applied between the substrates (102).
Further, it is determined whether or not blue is to be displayed
(104). If blue is to be displayed, the application voltage V (-Vc')
is applied between the substrates (106), and thereafter, the
application voltage V (Vm') is applied between the substrates
(108), and thereafter, the application voltage V (-Vy') is applied
between the substrates (110).
Moreover, it is determined whether or not green is to be displayed
(112). If green is to be displayed, the application voltage V
(-Vc') is applied between the substrates (114), and thereafter, the
application voltage V (Vy') is applied between the substrates
(116).
Further, it is determined whether or not black or grey is to be
displayed (118). If black or grey is to be displayed, the
application voltage V (-Vc') is applied between the substrates
(120), and thereafter, the application voltage V (Vm') is applied
between the substrates (122).
Moreover, it is determined whether or not yellow is to be displayed
(124). If yellow is to be displayed, the application voltage V
(Vc') is applied between the substrates (126), and thereafter, the
application voltage V (-Vm') is applied between the substrates
(128), and thereafter, the application voltage V (Vy') is applied
between the substrates (130).
Further, it is determined whether or not no display is to be
carried out (132). If no display is to be carried out, the
application voltage V (Vc') is applied between the substrates
(134), and thereafter, the application voltage V (-Vm') is applied
between the substrates (136).
Moreover, it is determined whether or not magenta is to be
displayed (138). If magenta is to be displayed, the application
voltage V (Vc') is applied between the substrates (140), and
thereafter, the application voltage V (-Vy') is applied between the
substrates (142).
On the other hand, if magenta is not to be displayed nor any of the
aforementioned colors, it is determined that red is to be
displayed, and the application voltage V (Vc') is applied between
the substrates (144).
Namely, in the exemplary embodiment, by applying, between the
substrates, the voltage which has the largest absolute value of the
voltage range which is largest among the voltage ranges required in
order for the respective colored particles to move, the three types
of colored particles 32 move toward the substrates corresponding to
the respective polarities thereof. Therefore, by using this as a
reference, the voltages which are required in order for the
respective colored particles to move are applied. In this way, as
compared with a case in which driving is carried out from a state
in which the respective colored particles 32 are being all mixed
together, there is little interaction, and control of the movement
of the respective colored particles 32 is easy. Accordingly, as
compared with a case in which driving is carried out from a state
in which the respective colored particles 32 are being all mixed
together, colors are displayed with color mixing suppressed.
Further, even in a case in which, from a state in which the
respective colored particles 32 were disposed so as to be mixed
together, driving were to be selectively carried out at a voltage
within the voltage range required for moving one type of the
colored particles 32, electrostatic force which pushes the colored
particles against a substrate would be applied to at least one type
of the colored particles which was not selected.
Although gradation display is not mentioned in particular in the
above, because the display density is changed as shown in FIG. 2 by
selecting a voltage within the voltage range in which the
corresponding type of colored particle moves, the gradations of the
respective colors can be controlled by selecting the voltages
appropriately. For example, to explain a method of display in a
case in which gradation of cyan is to be displayed, firstly,
application voltage (-Vc') is applied and cyan is displayed, and
thereafter, application voltage between Vc.ltoreq.V.ltoreq.Vc' is
applied in accordance with the gradation for which display is
desired. At this time, because the magenta particles 32M and the
yellow particles 32Y move toward the display substrate 18 side, by
applying application voltage -Vm', the magenta particles 32M and
the yellow particles 32Y are returned to the back surface substrate
28 side, and cyan gradation can be displayed. Or, cyan gradation
can be displayed even if application voltage Vc' is applied and the
cyan particles are moved toward the back surface substrate side
(i.e., red is displayed), and thereafter, a voltage of
-Vc'.ltoreq.V.ltoreq.-Vc is applied in accordance with the
gradation for which display is desired. Further, although an
example of the gradation display method has been described,
gradation display of the respective colors is possible by
appropriately selecting and applying the application voltages, and
therefore, gradation may be displayed by another gradation display
method.
Further, in the above-described first exemplary embodiment, there
is described an example in which the magnitudes of the absolute
values of the voltage ranges are set to be in the order of the cyan
particles 32C the magenta particles 32M and the yellow particles
32Y, and the cyan particles 32C whose absolute values of the
voltage range are the largest are made to be the opposite polarity
of the other colored particles 32. However, the embodiment is not
limited to the same. For example, the magnitudes of the absolute
values of the voltage ranges may be set to be in the order of the
yellow particles 32Y, the magenta particles 32M and the cyan
particles 32C, and the magenta particles 32M which are second in
the order of the magnitudes of the absolute values of the voltage
ranges may be made to be the polarity opposite the other colored
particles 32. Or, the magnitudes of the absolute values of the
voltage ranges may be set to be in the order of the cyan particles
32C, the magenta particles 32M and the yellow particles 32Y, and
the yellow particles 32Y which have the smallest absolute values of
the voltage ranges may be made to be opposite polarity of the other
colored particles 32. Or, the magnitudes of the absolute values of
the voltage ranges may be set to be in another order, and at least
one type be made to be the opposite polarity.
Here, description will be given of driving control of the image
display device in a case in which the magnitudes of the absolute
values of the voltage ranges are set in the order of the yellow
particles 32Y, the magenta particles 32M and the cyan particles
32C, and the magenta particles 32M which are second in the order of
the magnitudes of the absolute values of the voltage ranges are
made to be the opposite polarity of the other colored particles 32
(are made to be negative polarity).
First, when the voltage application section 40 applies the
application voltage V (-Vy'), which has the largest absolute values
of the voltage ranges required in order to move the respective
particles, between the transparent electrode 16 and the electrode
22 due to the control of the controller 42, the yellow particles
32Y and the cyan particles 32C which are positively polarized move
to the display substrate 18 side, and the magenta particles 32M
which are negatively polarized move to the back surface substrate
28 side. The state (1) in FIG. 5 thereby arises, and green, which
is a subtractive color mixture of yellow and cyan, is
displayed.
Further, when the voltage application section 40 applies the
application voltage V (Vy'), which has the largest absolute values
of the voltage ranges required in order to move the respective
particles, between the transparent electrode 16 and the electrode
22 due to the control of the controller 42, the magenta particles
32M which are negatively polarized move to the display substrate 18
side, and the yellow particles 32Y and the cyan particles 32C which
are positively polarized move to the back surface substrate 28
side. The state (2) in FIG. 5 thereby arises, and magenta is
displayed.
Moreover, from the state (1) in FIG. 5 (the green display state),
due to the voltage application section 40 applying the application
voltage V (Vc') between the transparent substrate 16 and the
electrode 22 due to the control of the controller 42, the cyan
particles 32C move to the back surface substrate 28 side. The state
(3) in FIG. 5 thereby arises, and yellow is displayed.
Further, from the state (1) in FIG. 5 (the green display state),
due to the voltage application section 40 applying the application
voltage V (Vm') between the transparent substrate 16 and the
electrode 22 due to the control of the controller 42, the magenta
particles 32M move to the display substrate 18 side, and the cyan
particles 32C move to the back surface substrate 28 side. The state
(4) in FIG. 5 thereby arises, and red, which is a subtractive color
mixture of magenta and yellow, is displayed.
Further, from the state (4) in FIG. 5 (the red display state), due
to the voltage application section 40 applying the application
voltage V (-Vc') between the transparent substrate 16 and the
electrode 22 due to the control of the controller 42, the cyan
particles 32C move to the display substrate 18 side. The state (5)
in FIG. 5 thereby arises, and black or grey, which is a subtractive
color mixture of cyan, magenta and yellow, is displayed.
Further, from the state (2) in FIG. 5 (the magenta display state),
due to the voltage application section 40 applying the application
voltage V (-Vm') between the transparent substrate 16 and the
electrode 22 due to the control of the controller 42, the magenta
particles 32M move to the back surface substrate 28 side, and the
cyan particles 32C move to the display substrate 18 side. The state
(6) in FIG. 5 thereby arises, and cyan is displayed.
Moreover, from the state (6) in FIG. 5 (the cyan display state),
due to the voltage application section 40 applying the application
voltage V (Vc') between the transparent substrate 16 and the
electrode 22 due to the control of the controller 42, the cyan
particles 32C move to the back surface substrate 28 side. The state
(7) in FIG. 5 thereby arises, and a non-display state arises. Note
that, at this time, if the dispersion liquid 24 is colored, the
color of the dispersion liquid 24 is displayed. For example, if the
dispersion liquid 24 is colored to white, white display becomes
possible.
Further, from the state (2) in FIG. 5 (the magenta display state),
due to the voltage application section 40 applying the application
voltage V (-Vc') between the transparent substrate 16 and the
electrode 22 due to the control of the controller 42, the cyan
particles 32C move to the display substrate 18 side. The state (8)
in FIG. 5 thereby arises, and blue, which is a subtractive color
mixture of cyan and magenta, is displayed.
Next, description will be given of driving control in a case in
which the magnitudes of the absolute values of the voltage ranges
are set in the order of the cyan particles 32C, the magenta
particles 32M and the yellow particles 32Y, and the yellow
particles 32Y which have the smallest absolute values of the
voltage ranges are made to be the opposite polarity of the other
colored particles 32 (are made to be negative polarity).
First, when the voltage application section 40 applies the
application voltage V (-Vc'), which has the largest absolute values
of the voltage ranges required in order to move the respective
particles, between the transparent electrode 16 and the electrode
22 due to the control of the controller 42, the cyan particles 32C
and the magenta particles 32M which are positively polarized move
to the display substrate 18 side, and the yellow particles 32Y
which are negatively polarized move to the back surface substrate
28 side. The state (1) in FIG. 6 thereby arises, and blue, which is
a subtractive color mixture of cyan and magenta, is displayed.
Further, when the voltage applying section 40 applies the
application voltage V (Vc'), which has the largest absolute values
of the voltage ranges required in order to move the respective
particles, between the transparent electrode 16 and the electrode
22 due to the control of the controller 42, the yellow particles
32Y which are negatively polarized move to the display substrate 18
side, and the cyan particles 32C and the magenta particles 32M
which are positively polarized move to the back surface substrate
28 side. The state (2) of FIG. 6 thereby arises, and yellow is
displayed.
Moreover, from the state (1) in FIG. 6 (the blue display state),
due to the voltage application section 40 applying the application
voltage V (Vy') between the transparent substrate 16 and the
electrode 22 due to the control of the controller 42, the yellow
particles 32Y move to the display substrate 18 side. The state (3)
in FIG. 6 thereby arises, and black or grey, which is a subtractive
color mixture of cyan, magenta and yellow, is displayed.
Further, from the state (1) in FIG. 6 (the blue display state), due
to the voltage application section 40 applying the application
voltage V (Vm') between the transparent substrate 16 and the
electrode 22 due to the control of the controller 42, the magenta
particles 32M move to the back surface substrate 28 side, and the
yellow particles 32Y move to the display substrate 18 side. The
state (4) in FIG. 6 thereby arises, and green, which is a
subtractive color mixture of cyan and yellow, is displayed.
Moreover, from the state (4) in FIG. 6 (the green display state),
due to the voltage application section 40 applying the application
voltage V (-Vy') between the transparent substrate 16 and the
electrode 22 due to the control of the controller 42, the yellow
particles 32Y move to the back surface substrate 28 side. The state
(5) in FIG. 6 thereby arises, and cyan is displayed.
Further, from the state (2) in FIG. 6 (the yellow display state),
due to the voltage application section 40 applying the application
voltage V (-Vm') between the transparent substrate 16 and the
electrode 22 due to the control of the controller 42, the magenta
particles 32M move to the display substrate 18 side, and the yellow
particles 32Y move to the back surface substrate 28 side. The state
(6) in FIG. 6 thereby arises, and magenta is displayed.
Moreover, from the state (6) in FIG. 6 (the magenta display state),
due to the voltage application section 40 applying the application
voltage V (Vy') between the transparent substrate 16 and the
electrode 22 due to the control of the controller 42, the yellow
particles 32Y move to the display substrate 18 side. The state (7)
in FIG. 6 thereby arises, and red, which is a subtractive color
mixture of magenta and yellow, is displayed.
Further, from the state (2) in FIG. 6 (the yellow display state),
due to the voltage application section 40 applying the application
voltage V (-Vy') between the transparent substrate 16 and the
electrode 22 due to the control of the controller 42, the yellow
particles 32Y move to the back surface substrate 28 side. The state
(8) in FIG. 6 thereby arises, and a non-display state arises. Note
that, at this time, if the dispersion liquid 24 is colored, the
color of the dispersion liquid 24 is displayed. For example, if the
dispersion liquid 24 is colored to white, white display becomes
possible.
Second Exemplary Embodiment
An image display device relating to a second exemplary embodiment
will be described next. FIG. 7 is a drawing showing the structure
of the image display device relating to the second exemplary
embodiment.
In the first exemplary embodiment, description is given of a case
in which three types of the colored particles 32 of the same size
are enclosed between substrates and respectively move between the
substrates. In the second exemplary embodiment, one type of colored
particles among the three types of colored particles is made to be
large-diameter colored particles 34 whose particle diameter is
greater than the other colored particles 32, and the colored
particles 32 other than the large-diameter colored particles 34
move between the substrates. In the following description, only
points which are different from the first exemplary embodiment will
be explained.
In the second exemplary embodiment, the large-diameter colored
particles 34 are colored to white, and the colored particles 32 are
white particles 32W and black particles 32K. However, the
embodiment is not limited to the same, and the particles may be
colored to other colors.
Particles whose particle diameters are larger than the colored
particles 32 are used as the large-diameter colored particles 34.
The colored particles 32 must pass through the spaces between the
large-diameter colored particles 34. Therefore, particles whose
particle diameter is 10 times or more (and preferably 20 times or
more) greater than the colored particles 32 can be used as the
large-diameter colored particles 34. However, because the
large-diameter colored particles 34 are enclosed between the
substrates, the particle diameter thereof is smaller than the
distance between the substrates.
In cases in which the diameters of the colored particles 32 are
substantially uniform, it suffices for the size of the
large-diameter colored particles 34 to be 10 times or more greater
than the colored particles 32. However, in cases in which there is
dispersion in the diameters of the colored particles 32 and larger
colored particles 32 are included, the size of the large-diameter
colored particles 34 being 20 times or more greater eliminates
clogging of the colored particles 32 between the large-diameter
colored particles 34. Note that, in the exemplary embodiment,
"substantially uniform" means that the dispersion in particle
diameters is small. For example, dispersion which is about .+-.50%
of the average particle diameter is "substantially uniform". (In a
case in which the average particle diameter is 1 .mu.m,
substantially all of the particles fall between 0.5 .mu.m to 1.5
.mu.m. For "substantially all", a standard deviation of 2.sigma.
(95.4%) for example can be used as the standard.)
If the particle diameter of the large-diameter colored particles 34
is too small, there are cases in which spaces between the
particles, through which the colored particles 32 can move, cannot
be sufficiently ensured. Further, if the particle diameter is too
large, the space between the substrates becomes large, and there
are cases in which the structure becomes high voltage and a
decrease in the display speed arises. Note that, if the volume
average particle diameter of the large-diameter colored particles
34 is around 10 .mu.m, colored particles 32 of a volume average
particle diameter of from several tens of nm to several hundred nm
can move through the spaces between the large-diameter colored
particles 34.
For example, particles in which a white pigment such as titanium
oxide, silicon oxide, zinc oxide, or the like is dispersed in
polystyrene, polyethylene, polypropylene, polycarbonate, PMMA
(polymethylmethacrylate), an acrylic resin, a phenol resin, a
formaldehyde condensate, or the like can be used as the
large-diameter colored particles 34. Further, resin particles which
contain, for example, a pigment or a dye of the desired color as
the color of the large-diameter colored particles 34 can be used.
For the pigment or dye, for example, a general pigment or dye which
is used in printing inks or color toners can be used.
The enclosing of the large-diameter colored particles 34 between
the substrates is carried out by, for example, an
electrophotographic method, a toner jetting method, or the like.
Further, in a case of fixing the large-diameter colored particles
34, the fixing can be carried out while maintaining the spaces
between the particles by, for example, enclosing the large-diameter
colored particles 34, and thereafter, carrying out heating (and
pressurizing if needed), and softening the particle group surface
layers of the large-diameter colored particles 34 and fusing them
together.
Note that the disclosure of JP-A No. 2001-312225 for example can be
applied for the respective members structuring the image display
medium.
Even after the application of voltage between the substrates is
stopped, the colored particles 32 are maintained in the state of
the time when the voltage was applied, due to van der Waals force
and image forces.
Further, in the exemplary embodiment, the large-diameter colored
particles 34 which are colored white have a charge characteristic
which is the opposite polarity of the colored particles 32 which
are the same color as the large-diameter colored particles 34, or a
charge characteristic which is the same polarity as the colored
particles 32 which are a different color than the large-diameter
colored particles 34.
In the exemplary embodiment, the white particles 32W have a
positive charge characteristic, and the large-diameter colored
particles 34, which are the same color as the white particles 32W,
have a negative charge characteristic which is the opposite
polarity of the white particles 32W. Note that the black particles
32K may have a negative charge characteristic, and the
large-diameter colored particles 34 may be polarized negatively
which is the same polarity as the black particles 32K. Further,
FIG. 7 shows a state in which the large-diameter colored particles
34 are negatively polarized.
Next, an example of display driving control of the image display
device, which relates to the second exemplary embodiment and is
structured as described above, will be described. Note that,
hereinafter, in order to simplify explanation, description will be
given of the electrode 22 at the back surface substrate 28 side
being ground (0 V) and voltage being applied to the transparent
electrode 16 at the display substrate 18 side. Further, in the
display driving control of the exemplary embodiment, white or black
display is carried out by applying a positive or negative
predetermined voltage between the transparent substrate 16 and the
electrode 22.
In the second exemplary embodiment, when the voltage application
section 40 applies a positive predetermined voltage between the
transparent substrate 16 and the electrode 22 due to the control of
the controller 42, the white particles 32W which are negatively
polarized move to the back surface substrate 28 side and the black
particles 32K which are positively polarized move to the display
substrate 18 side, such that the state shown in FIG. 7 arises.
Accordingly, the black particles 32K can be observed from the
display substrate 18 side, and black is displayed.
On the other hand, when the voltage application section 40 applies
a negative predetermined voltage between the transparent substrate
16 and the electrode 22 due to the control of the controller 42,
the black particles 32K which are positively polarized move to the
back surface substrate 28 side and the white particles 32W which
are negatively polarized move to the display substrate 18 side. In
this way, the white particles 32W can be observed from the display
substrate 18 side, and white is displayed.
In the second exemplary embodiment, the white particles 32W, which
are the same color as the large-diameter colored particles 34, have
the opposite polarity. Therefore, due to the electrostatic
attraction between the white particles 32W and the large-diameter
colored particles 34, the white particles 32W which have peeled
away from the substrate surface are held at the surfaces of the
nearby large-diameter colored particles 34 which are colored to the
same white color, and color mixing is suppressed and the image
maintainability is improved.
Further, because the black particles 32K, which are a different
color than the large-diameter colored particles 34, have the same
polarity, due to electrostatic repulsion, the black particles 32K
which are a different color can be prevented from adhering to the
surfaces of the large-diameter colored particles 34. Moreover, due
to the electrostatic repulsion between the black particles 32K and
the surfaces of the large-diameter colored particles 34, force
which pushes the black particles 32K against the substrate surface
acts on the black particles 32K which are the same polarity as the
large-diameter colored particles 34, and color mixing is suppressed
and the image maintainability is improved.
Note that with the large-diameter colored particles 34 of the
exemplary embodiment, another one type of the colored particles 32
may be enclosed between the substrates as shown in FIG. 8. Namely,
the large-diameter colored particles 34 may be enclosed between the
substrates of the image display device of the first exemplary
embodiment which has the three types of colored particles 32. The
display driving control in this case can be made to be similar to
that of the first exemplary embodiment. At this time, the
large-diameter colored particles 34 may be a color other than
white, and may be unpolarized particles. Further, other colors than
the first exemplary embodiment may be appropriately used as the
colors of the three types of colored particles 32.
Further, in the exemplary embodiment, as shown in FIG. 9,
multicolor particles which are painted two or more colors (in FIG.
9, bicolor particles 36 which are painted two colors) may be used
instead of the large-diameter colored particles 34. At this time,
the bicolor particles 36 may be the same colors as the colors of
the colored particles 32, or may be different colors. Further, the
bicolor particles 36 may be painted such that the surface areas
which are painted in the two colors are respectively different
surface areas, or same surface areas. Still further, at least a
portion of the bicolor particle 36 which is offset from the center
of gravity has positive or negative polarity, and the bicolor
particle 36 rotates in accordance with the electric field which is
applied between the substrates.
In the same way as the large-diameter colored particles 34,
particles whose particle diameters are larger than the colored
particles 32 are used as the bicolor particles 36, and the colored
particles 32 must move through the spaces between the bicolor
particles 36. Therefore, particles whose particle diameter is 10
times or more (and preferably 20 times or more) greater than the
colored particles 32 are used as the bicolor particles 36. However,
because the bicolor particles 36 are enclosed between the
substrates, the particle diameter thereof is smaller than the
distance between the substrates. In cases in which the diameters of
the colored particles 32 are substantially uniform, it suffices for
the size of the bicolor particles 36 to be 10 times or more greater
than that of the colored particles 32. However, in cases in which
there is dispersion in the diameters of the colored particles 32
and larger colored particles 32 are included, the size of the
bicolor particles 36 being 20 times or more greater eliminates
clogging of the colored particles 32 between the bicolor particles
36. If the particle diameter of the bicolor particles 36 is too
small, there are cases in which spaces between the particles,
through which the colored particles 32 can move, cannot be
sufficiently ensured. Further, if the particle diameter is too
large, the space between the substrates becomes large, and there
are cases in which the structure becomes high voltage and a
decrease in the display speed arises. Note that, if the volume
average particle diameter of the bicolor particles 36 is around 10
.mu.m, the colored particles 32 of a volume average particle
diameter of from ten nm to several hundred nm can move through the
spaces between the bicolor particles 36.
If the size of the bicolor particles 36 is too small, it becomes
difficult to obtain the rotational force which is due to the
electric field between the substrates, and the application voltage
required to rotate the bicolor particles 36 becomes extremely
large. For example, in order to drive the bicolor particles 36 at
an application voltage of several tens of V, a size of greater than
or equal to 10 .mu.m is required. Further, if the size of the
bicolor particles 36 is too large, the distance between the
substrates becomes large, and the application voltage becomes high
just the same. In consideration thereof, the size of the bicolor
particles 36 may set to a size of 10 .mu.m to 100 .mu.m. Note that
the volume average particle diameter of the multicolor particles
(the bicolor particles 36 in FIG. 9) is measured by the Laser
Scattering Particle Size Distribution Analyzer LA-920 manufactured
by Horiba, Ltd.
Note that, because the transparence of the bicolor particles 36 is
low, from the standpoint of the ability to generate color, the
bicolor particles 36 may be positioned at the back surface side of
the colored particles as seen from the display substrate side,
rather than being mixed-in together among the colored particles 32.
If the bicolor particles 36 are made to be larger than the colored
particles 32 and the colored particles 32 move through the spaces
between the bicolor particles 36, the colored particles 32 can be
moved to the display substrate surface and the bicolor particles 36
can be disposed behind them. Further, in the case of actually
driving and rotating the bicolor particles 36, a driving voltage
which is much higher than that for moving the colored particles 32
is required. However, if the bicolor particles 36 are made to be
large, a large rotational moment is obtained. Therefore, making the
bicolor particles 36 large is effective in lowering the driving
voltage and in improving the display ability and the
reliability.
For the white portions of the bicolor particles 36, there can be
used particles in which a white pigment such as, for example,
titanium oxide, silicon oxide, zinc oxide, or the like is dispersed
in polystyrene, polyethylene, polypropylene, polycarbonate, PMMA,
an acrylic resin, a phenol resin, a formaldehyde condensate, or the
like. For the chromatic portions of the bicolor particles 36, for
example, if the color is a color among RGB or YMC, a general
pigment or dye which is used in printing inks or color toners can
be used.
The enclosing of the bicolor particles 36 between the substrates is
carried out by, for example, an electrophotographic method, a toner
jetting method or the like. Further, members disclosed in JP-A No.
2001-312225 for example can be used as the respective members
structuring the image display medium.
By making the voltage range (absolute values) required in order to
rotate the bicolor particles 36 and the voltage ranges (absolute
values) required in order to move the respective colored particles
32 be respectively different characteristics, each of the types of
particles can be driven independently of one another. By making the
voltage range (absolute values) required for the bicolor particles
36 to rotate greater than the voltage ranges (absolute values)
required for the respective colored particles to move, and by
carrying out display control by using, as the reference state, the
state in which a voltage required to rotate the bicolor particles
36 is applied, display driving is stable as compared with a case in
which this structure is not employed. Note that the application
voltages required in order for the three types of colored particles
32 to move can be controlled by, for example, the charge amount,
the particle diameter, or the shape or properties of the particle
surface, or the like. Further, the application voltage required in
order for the bicolor particles 36 to rotate can be controlled by
the charge amount, the particle diameter, the viscosity of the
solvent, or the like. The "voltage range required to rotate the
bicolor particles" means a voltage range from the voltage required
in order for the particles to start rotating, up to a voltage at
which, when the voltage and the voltage application time are
further increased from the start of rotation, no change arises in
the display density and the display density is saturated. Further,
the method of measuring the display density is as described in the
case of the colored particles of the first exemplary
embodiment.
In order to respectively drive the three types of colored particles
32 and the bicolor particles 36 independently, the voltage ranges
required to move (or to rotate) substantially all of the respective
particles are set so as to not overlap one another. In this way,
the respective colored particles 32 and the bicolor particles 36
can be driven independently. The respective colors can be displayed
by selectively applying, between the substrates, voltages required
for the three types of colored particles 32 to move and voltage
required for the bicolor particles to rotate, by using, as the
reference, a state in which the maximum voltage is applied between
the substrates, among the voltage ranges required in order for the
three types of colored particles 32 to move and the voltage range
required in order for the bicolor particles 36 to rotate. Note that
"substantially all" means that, because there is dispersion in the
characteristics of the colored particles 32 and the bicolor
particles 36, the characteristics of some of the colored particles
32 differ to an extent of not contributing to the display
characteristic. Namely, when the voltage and the voltage
application time are further increased from the start of movement
of the particles, there is a state in which no change arises in the
display density and the display density is saturated.
Further, "maximum voltage of the voltage range required in order
for the multicolor particles to rotate" means a voltage at which,
when the voltage and the voltage application time are further
increased from the aforementioned start of rotation, no change
arises in the display density and the display density is
saturated.
As shown in FIG. 10, a porous body 46, which is structured of
silicone rubber or the like and in which a migration liquid such as
silicone oil or the like is filled, may be applied to the image
display medium of FIG. 9 instead of the dispersion liquid 24. In
this case, the porous body 46 can be produced by, for example,
kneading the bicolor particles 36 in an elastomer which contains a
liquid silicone rubber, and thereafter, gelling and fixing, and
thereafter, enclosing a silicone oil in which the colored particles
32 are dispersed. Further, minute cavities 48, which are of a size
that does not impede the rotational motion of the bicolor particles
36, are formed at the peripheries of the bicolor particles 36. The
porous body 46 has a mesh structure having openings of sizes
through which the colored particles 32 can move. In this way, the
colored particles 32 can move between the substrates through these
openings that are filled with the migration liquid.
Moreover, as shown in FIG. 11, the bicolor particles 36 of the
image display medium of FIG. 9 may be enclosed in a rotatable state
in transparent capsules 50 which are filled with a transparent,
encapsulated migration liquid. In this case, the application
voltages for moving the colored particles 32 and the application
voltage for rotating the bicolor particles 36 can be adjusted by
selecting the respective compositions and viscosities of the
dispersion liquid 24 between the substrates and the encapsulated
migration liquid.
Note that, although three types of the colored particles 32 are
enclosed in the dispersion liquid 24 between the substrates in the
above-described first exemplary embodiment, the embodiment is not
limited to the same. For example, as shown in FIG. 12A, the colored
particles 32 may be enclosed in transparent capsules 54 in which a
migration liquid 52 is enclosed. Further, also in cases in which
the bicolor particles 36 are included as well, as shown in FIG.
12B, the bicolor particles 36 also may be enclosed within the
transparent capsules 54.
In the above second exemplary embodiment, the large-diameter
colored particles 34 are described as an example of a reflecting
member, but the embodiment is not limited to the same. For example,
a resin sheet or a nonwoven fabric or the like may be used as a
reflecting member. By using a resin sheet or a nonwoven fabric as
the reflecting member, background colors such as white or the like
can be displayed more uniformly than with the large-diameter
colored particles 34, and the image display medium can be made to
be more thin, and manufacturing is easy. Examples of materials
structuring the resin sheet or nonwoven fabric include
polyethylene, polystyrene, polyester, polyacryl, polypropylene,
fluorinated resins such as polytetrafluoroethylene (PTFE), and the
like. Polypropylene and PTFE resin can be particularly used because
it is difficult for the colored particles 32 to adhere thereto. If
a reflecting member 38 is structured by a nonwoven fabric, it
suffices to structure the nonwoven fabric as an aggregation of
fibers formed from these materials.
The porosity of the reflecting member can be made greater than or
equal to 50% and less than or equal to 80% because both a good
passage performance of the colored particles 32 passing through,
and a good color generating ability of the image display medium 12
can be achieved. Further, the average hole diameter of the holes of
the reflecting member through which the colored particles 32 pass
is not particularly limited provided that it is a size such that
the particles structuring the colored particles 32 can pass
therethrough. However, the average particle diameter of the colored
particles 32 is preferably within a range of greater than or equal
to 1.2 times to less than or equal to 10,000 times the volume
average primary particle diameter of the colored particles 32, and
more preferably within a range of greater than or equal to 2 times
to less than or equal to 1000 times. If the average hole diameter
of the reflecting member is less than 1.2 times the volume average
primary particle diameter of the colored particles 32, there are
cases in which it is difficult for the respective particles which
structure the colored particles 32 to move through the holes. If
greater than 10,000 times, the problem of a deterioration in color
generation may arise because the spaces become large.
If the reflecting member 38 is structured by a nonwoven fabric, the
basis weight of the fibers structuring the nonwoven fabric may be
within the range of greater than or equal to 10 g/m.sup.2 and less
than or equal to 100 g/m.sup.2, and preferably the basis weight may
be within the range of greater than or equal to 20 g/m.sup.2 and
less than or equal to 50 g/m.sup.2 , in order to make the passage
rate of the colored particles 32 good and to make the thickness of
the image display medium 12 thin. Further, the diameters of the
fibers structuring the nonwoven fabric may be within a range of
greater than or equal to 0.1 .mu.m and less than or equal to 20
.mu.m, and preferably greater than or equal to 0.1 .mu.m and less
than or equal to 3 .mu.m, because a sufficient surface area is
ensured and physical strength is ensured.
The foregoing description of the exemplary embodiments of the
present invention has been provided for the purpose of illustration
and description. It is not intended to be exhaustive or to limit
the invention to the precise form disclosed herein. Obviously, many
modifications and variations will be apparent to a practitioner
skilled in the art. The exemplary embodiments were chosen and
described in order to best explain the principles of the invention
and its practical applications, thereby enabling others skilled in
the art to understand the invention according to various
embodiments and with various modifications as are suited to the
particular use contemplated. It is intended that the scope of the
invention be defined by the following claims and their
equivalents.
* * * * *